First: a disclaimer...My sewing room is in the basement. I have yet to purchase extra lighting for taking pictures. Therefore, they are a bit dark. And..my ironing board is very, very old and well used, not dirty. And, my pressing board is also well used. Given all of this, the tutorial is a good one and produces sound results. :)
Materials: poster board, permanent drawing tool, garment needing hemmed, sewing machine
Now for the tutorial:
*First make a pressing board. (You can also buy such a tool made out of metal.)
I used a piece of poster board. You can use anything of that weight. (I've had mine and been using it a lot for a year, and it seems to be holding up very well, except for a little bit of darkening, as you can see.)
*Cut a square about 12 x 12 or what ever size you want.
*Use a permanent drawing tool. I tested and used an ink pen. You don't want the ink to come off onto your fabric (even with steam). So test if on a scrap before drawing lines and using it on a garment.
Measure up from the edge 1/4" and, with a straight edge, draw a line. Label it 1/4". Repeat this process for any other common pressing measurements you use. (I commonly use 1/4", 1", and 1 1/4" in my patterns. So these are the lines I'd have. Although, I've put a few others on mine also.)* Lay your fabric onto your ironing board, wrong side facing up. Roll the raw edge (to be hemmed) over the pressing board. Match the raw edge up to the appropriate line on the pressing board and press.
*Roll the pressed edge over the pressing board again and match the edge to the appropriate line and press again. This encases the raw edge and gives a nice straight edge ready to sew.
*Sew along the top edge of the pressed area with a coordinating thread. (I used a contrasting thread so you could see it more easily.) Press again to finish.
Using the pressing board guarantees that you fold down an exact amount as you prepare your hem, and eliminates the possibility for error if you were to measure and pin every few inches. Also, if your cut edge happens to be a bit cooked you'll notice it as you fold the fabric over the board and can adjust accordingly. I don't know about you, but I don't always cut straight and sometimes my "straight edges" have a bit of a wave. lol.
I've used this technique on an edge with a slight curve, like an a-line skirt or dress, with some success. Since there is a slight curve to the hemline and my pressing board is straight, it requires a bit of easing while pressing and doesn't provide a completely straight hem. However, if anyone is ever close enough to myself or one of my children to tell that it's not completely straight...I'll have to smack them. ;)